An estimated 53 million people, mostly women, are employed as domestic workers in private households around the world.

While domestic workers are now considered crucial to the smooth running of national economies, as a workforce they remain one of the most vulnerable to exploitation, abuse and modern-day slavery.

Human rights campaigners have catalogued a litany of exploitation faced by domestic workers at the hands of their employers, including forced labour, rape, daily beatings and being forced to work long hours with no breaks.

According to the International Domestic Workers Federation, employers who exploit or underpay their domestic workers make $8bn (£5.1bn) a year in illegal profits.

The vulnerability of domestic workers is rooted in the nature of their work – typically undertaken behind closed doors in private homes far from their own communities – and the lack of legal protection they receive.

Though critical to the functioning of national economies, only 10% of domestic workers have the same basic labour rights as other sectors. A quarter of all domestic workers are not afforded any legal rights at all.

“I think one of the problems is that there is an assumption that domestic work is just done by women. There is no inherent value attached to this work by employers or by governments,” says Ai-jen Poo, director of the National Domestic Workers Alliance. “The discrimination and isolation these women face is compounded by their absence from many labour laws. It means they can be effectively disappeared behind closed doors in private homes, with nobody aware of what is happening to them.”

In some countries, including the UK, domestic workers are bound to their employers through tied-visa systems, which prevents them from leaving to seek employment elsewhere even if they face violence and exploitation.

Upon arrival in any of these countries, domestic workers fall under the regional kafala system, meaning the consent of the “sponsor” family is required if they wish to leave their employment.

In countries that enforce the kafala system rigorously, such as Saudi Arabia and Qatar, it is illegal for domestic workers to flee abusive employers. Those who do risk being detained as “runaway” undocumented workers. They are unable to leave the country without the permission of their employers.

Human Rights Watch and others have documented horrendous abuse of maids and domestic servants in private households in the UAE, with widespread sexual violence, beatings, confiscation of passports and non-payment of wages.

Unmarried domestic workers who become pregnant can be charged with illicit relations and imprisoned with their babies. In Saudi Arabia, eight maids sheltering with their children at the Philippine Embassy in Riyadh could be jailed for illicit behaviour, even though some of them had been raped by their employers, according to the NGO Migrante International.

A 2012 survey of 3,000 domestic workers in Hong Kong, home to an estimated 320,000 domestic staff, found that 58% had reported verbal abuse, while 18% said they had been physically assaulted and 6% claimed to have suffered sexual abuse.

In the past few weeks, Hong Kong has been rocked by a landmark case in which the wealthy employer of an Indonesian domestic worker was convicted of 18 counts of inflicting grievous bodily harm.

Meanwhile, a survey of domestic workers in the US found that 25% were paid less than the minimum wage. A total of 10% said they weren’t paid anything at all.

In Australia, where an estimated 54,000 of Asia-Pacific’s 21 million-plus domestic workers are based, a Salvation Army report catalogued 16-hour days without breaks, non-payment of wages and physical violence. The study, published last year, concluded that private homes in Australia were becoming “prisons that people cannot leave”.

A 2013 study found that about 17% of child domestic workers were sexually abused in Bangladesh’s capital, Dhaka, while 83% suffered physical abuse from their employers. In Nigeria, Unicef, the UN children’s fund, reports that hundreds of thousands of children work as domestic servants, which puts them at risk of sexual violence and other forms of abuse. .

In Indonesia, where national laws setting the minimum working age are not enforced for domestic labour, child domestic workers earn as little as 1p an hour.